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Structural color pigments offer an efficient, sustainable, and environmentally friendly approach to obtain waterborne polymer coatings. We developed polymer-based spherical photonic pigments to incorporate in aqueous dispersions of polymer nanoparticles used to obtain waterborne polymer films. Our spherical photonic pigments are assembled from polymer nanoparticles and are highly stable in water dispersion, maintaining their optical properties in the final polymer films. Unlike conventional dyes and pigments, which are prone to photobleaching because they are based on the absorption of light, photonic pigments rely on the selective reflection of light by their nanostructure and therefore are not photodegraded. Furthermore, different colors can be obtained from the same materials, changing only their nanostructure, in this case, the size of the polymer nanoparticles. Our novel spherical photonic pigments are noniridescent and can be incorporated in aqueous polymer nanoparticle dispersions without deteriorating their structure to produce waterborne polymer coatings with structural color. This approach for structural colored waterborne polymer coatings is efficient, simple, and environmentally friendly, offering excellent prospects for application in paints and coatings.
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Fluorescent silica nanoparticles with a polymer shell of poly (D, L-lactide-co-glycolide) (PLGA) can provide traceable cell-triggered delivery of the anticancer drug doxorubicin (DOX), protecting the cargo while in transit and releasing it only intracellularly. PLGA with 50:50 lactide:glycolide ratio was grown by surface-initiated ring-opening polymerization (ROP) from silica nanoparticles of ca. 50 nm diameter, doped with a perylenediimide (PDI) fluorescent dye anchored to the silica structure. After loading DOX, release from the core-shell particles was evaluated in solution at physiological pH (7.4), and in human breast cancer cells (MCF-7) after internalization. The hybrid silica-PLGA nanoparticles can accommodate a large cargo of DOX, and the release in solution (PBS) due to PLGA hydrolysis is negligible for at least 72 h. However, once internalized in MCF-7 cells, the nanoparticles release the DOX cargo by degradation of the PLGA. Accumulation of DOX in the nucleus causes cell apoptosis, with the drug-loaded nanoparticles found to be as potent as free DOX. Our fluorescently traceable hybrid silica-PLGA nanoparticles with cell-triggered cargo release offer excellent prospects for the controlled delivery of anticancer drugs, protecting the cargo while in transit and efficiently releasing the drug once inside the cell.
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Antineoplásicos , Nanopartículas , Humanos , Dióxido de Silicio , Doxorrubicina/farmacología , Doxorrubicina/química , Nanopartículas/química , Polímeros/química , Portadores de Fármacos/químicaRESUMEN
The need for new therapeutic approaches for triple-negative breast cancer is a clinically relevant problem that needs to be solved. Using a multi-targeting approach to enhance cancer cell uptake, we synthesized a new family of ruthenium(II) organometallic complexes envisaging simultaneous active and passive targeting, using biotin and polylactide (PLA), respectively. All compounds with the general formula, [Ru(η5-CpR)(P)(2,2'-bipy-4,4'-PLA-biotin)][CF3SO3], where R is -H or -CH3 and P is P(C6H5)3, P(C6H4F)3 or P(C6H4OCH3)3, were tested against triple-negative breast cancer cells MDA-MB-231 showing IC50 values between 2.3-14.6 µM, much better than cisplatin, a classical chemotherapeutic drug, in the same experimental conditions. We selected compound 1 (where R is H and P is P(C6H5)3), for further studies as it was the one showing the best biological effect. In a competitive assay with biotin, we showed that cell uptake via SMVT receptors seems to be the main transport route into the cells for this compound, validating the strategy of including biotin in the design of the compound. The effects of the compound on the hallmarks of cancer show that the compound leads to apoptosis, interferes with proliferation by affecting the formation of cell colonies in a dose-dependent manner and disrupts the cell cytoskeleton. Preliminary in vivo assays in N: NIH(S)II-nu/nu mice show that the concentrations of compound 1 used in this experiment (maximum 4 mg/kg) are safe to use in vivo, although some signs of liver toxicity are already found. In addition, the new compound shows a tendency to control tumor growth, although not significantly. In sum, we showed that compound 1 shows promising anti-cancer effects, bringing a new avenue for triple-negative breast cancer therapy.
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Molecular permeability through polymer brush chains is implicated in surface lubrication, wettability, and solute capture and release. Probing molecular transport through polymer brushes can reveal information on the polymer nanostructure, with a permeability that is dependent on chain conformation and grafting density. Herein, we introduce a brush system to study the molecular transport of fluorophores from an aqueous droplet into the external "dry" polymer brush with the vapour phase above. The brushes consist of a random copolymer of N-isopropylacrylamide and a Förster resonance energy transfer (FRET) donor-labelled monomer, forming ultrathin brush architectures of about 35 nm in solvated height. Aqueous droplets containing a separate FRET acceptor are placed onto the surfaces, with FRET monitored spatially around the 3-phase contact line. FRET is used to monitor the transport from the droplet to the outside brush, and the changing internal distributions with time as the droplets prepare to recede. This reveals information on the dynamics and distances involved in the molecular transport of the FRET acceptor towards and away from the droplet contact line, which are strongly dependent on the relative humidity of the system. We anticipate our system to be extremely useful for studying lubrication dynamics and surface droplet wettability processes.
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Transferencia Resonante de Energía de Fluorescencia , Polímeros , Polímeros/química , Soluciones , Agua , HumectabilidadRESUMEN
The development of appropriate methods to correlate the structure and optical properties of colloidal photonic structures is still a challenge. Structural information is mostly obtained by electron, X-ray, or optical microscopy methods and X-ray diffraction, while bulk spectroscopic methods and low resolution bright-field microscopy are used for optical characterization. Here, we describe the use of reflectance confocal microscopy as a simple and intuitive technique to provide a direct correlation between the ordered/disordered structural morphology of colloidal crystals and glasses, and their corresponding optical properties.
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Highly efficient pH-modulated cargo release was achieved with a new hybrid nanocarrier composed of a mesoporous silica core with functionalized pores and a grafted pH-responsive crosslinked polymer shell of 2-(diisopropylamino)ethyl methacrylate (pKa ≈ 6.5). The retention/release performance of the system was optimized by a novel approach using selective functionalization of the silica pores to tune the carrier-cargo interaction and by tunning the amount of grafted polymer. The system features excellent retention of cationic cargo at low pH and a burst release at higher pH. This results from the expanded-collapsed conformation transition of the pH-responsive polymer shell and the simultaneous change in the interaction between the cargo and the polymer shell and the modified pore walls. At low pH, the electrostatic interaction of the cationic cargo with the protonated amine groups of the extended polymer shell retains the cargo, resulting in very low leakage (OFF state). At high pH, the electrostatic interaction with the cargo is lost (due to deprotonation of the polymer amine groups), and the polymer shell collapses, squeezing out the cargo in a burst release (ON state). Pore functionalization in combination with the stimuli-responsive polymer shell is a very promising strategy to design high-performance ON:OFF smart hybrid nanocarriers for stimuli-actuated cargo release, with great potential for application in the controlled release of drugs and other biologically active agents.
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Combining organic and inorganic components at a nanoscale is an effective way to obtain high performance coating materials with excellent chemical and physical properties. This review focuses on recent approaches to prepare hybrid nanostructured waterborne coating materials combining the mechanical properties and versatility of silica as the inorganic filler, with the flexural properties and ease of processing of the polymer matrix. We cover silica-polymer coupling agents used to link the organic and inorganic components, the formation of hybrid films from these silica-polymer nanostructures, and their different applications. These hybrid nanostructures can be used to prepare high performance functional coatings with different properties from optical transparency, to resistance to temperature, hydrophobicity, anti-corrosion, resistance to scratch, and antimicrobial activity.
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Mesoporous silica nanoparticles (MSNs) feature ideal structural properties and surface chemistry for use as nanocarriers of molecules, polymers and biomolecules in cutting-edge applications. One important challenge remaining in their preparation is the ability to tune their diameter in the range of a few tens of nanometers, with narrow size dispersity, preferably using a simple, sustainable and scalable synthetic process. This work presents a fully controllable low-temperature and purely aqueous sol-gel method to prepare MSNs with user-defined diameters from 15â¯nm to 80â¯nm and narrow size dispersity. The method also allows modification of the pore structure and offers the possibility of incorporating a luminescent species in the silica network for optical traceability. Control was achieved by tuning the colloidal stability of the assembly of cylindrical micelles that template the MSN synthesis. Using CTAB cylindrical micelles as template and sodium hydroxide (NaOH) as catalyst, precise diameter control was achieved either by changing the pH (that controls micelle surface charge) or by adding salt at constant pH (to tune the ionic strength and charge screening). This new sustainable MSN synthesis method provides full control over the nanoparticle diameters and can be used as a platform for the application of MSNs with user-defined sizes in different fields.
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The differentiation of adult stem cells is usually performed in vitro, by exposing them to specific factors. Alternatively, one can use nanocarriers containing such factors, to be internalized by the cells. In this work we have reduce the size of those carriers to the nanoscale, developing bioactive silica nanoparticles with diameters under 100â¯nm, containing calcium and phosphate ions (SiNPs-CaP). These ions, once released inside adult stem cells, induce bone cell proliferation and differentiation, and stimulate the expression of bone-related proteins in a single dose administration. The SiNPs-CaP nanomaterials were prepared through a sol-gel approach, and the ions added with a post-synthesis functionalization method. The synthesized SiNPs-CaP have narrow size distribution, good colloidal stability, and show high levels of ion incorporation. Furthermore, the SiNPs-CaP have good cytocompatibility and promote the osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSC), with alkaline phosphatase, osteopontin and osteocalcin production levels comparable to the ones obtained in standard osteogenic medium. The novel bioactive SiNPs-CaP are synthesized in a simple and fast manner and show the ability to promote osteogenic differentiation after a single dose administration, independently from external osteogenic inducers, showing great potential as carriers in bone tissue engineering applications.
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Calcio/administración & dosificación , Células Madre Mesenquimatosas/citología , Nanopartículas/química , Osteogénesis/efectos de los fármacos , Fosfatos/administración & dosificación , Fosfatasa Alcalina/metabolismo , Calcio/química , Calcio/farmacocinética , Diferenciación Celular/efectos de los fármacos , Células Cultivadas , Liberación de Fármacos , Humanos , Células Madre Mesenquimatosas/efectos de los fármacos , Nanopartículas/administración & dosificación , Osteocalcina/metabolismo , Osteogénesis/fisiología , Osteopontina/metabolismo , Tamaño de la Partícula , Fosfatos/química , Fosfatos/farmacocinética , Dióxido de Silicio/químicaRESUMEN
Among a variety of inorganic-based nanomaterials, mesoporous silica nanoparticles (MSNs) have several attractive features for application as a delivery system, due to their high surface areas, large pore volumes, uniform and tunable pore sizes, high mechanical stability, and a great diversity of surface functionalization options. We developed novel hybrid MSNs composed of a mesoporous silica nanostructure core and a pH-responsive polymer shell. The polymer shell was prepared by RAFT polymerization of 2-(diisopropylamino)ethyl methacrylate (pKa ~6.5), using a hybrid grafting approach. The hybrid nanoparticles have diameters of ca. 100 nm at pH < 6.5 and ca. 60 nm at pH > 6.5. An excellent control of cargo release is achieved by the combined effect of electrostatic interaction of the cargo with the charged silica and the extended cationic polymer chains at low pH, and the reduction of electrostatic attraction with a simultaneous collapse of the polymer chains to a globular conformation at higher pH. The system presents a very low (almost null) release rate at acidic pH values and a large release rate at basic pH, resulting from the squeezing-out effect of the coil-to-globule transition in the polymer shell.
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Mesoporous silica materials have demonstrated a vast spectrum of applications, stimulating an intensive field of study due to their potential use as nanocarriers. Nonetheless, when produced at the nanoscale, their structural characterization is hindered due to the re-arrangement of the pores. To address this issue, this work combines molecular dynamics simulations with electron microscopy computer simulations and experimental results to provide an insight into the structure of amorphous mesoporous silica nanoparticles. The amorphous silica model is prepared using a simple melt-quench molecular dynamics method, while the reconstruction of the mesoporous nanoparticles is carried out using a methodology to avoid false symmetry in the final model. Simulated scanning transmission electron microscopy images are compared with experimental images, revealing the existence of structural domains, created by the misalignment of the pores to compensate the surface tension of these spherical nanoparticles.
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A unique combination of molecular dynamics (MD) simulation and detailed size exclusion chromatography-multiangle light scattering (SEC-MALS) analysis is used to provide important a priori insights into the solution self-assembly of a well-defined and symmetric tetrablock copolymer with two acrylic acid (AA) outer blocks, two polystyrene (PS) inner blocks, and a trithiocarbonate (TTC) central group, prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. SEC-MALS experiments show that the copolymer forms aggregates in both tetrahydrofuran and N,N-dimethylformamide (DMF), even in the presence of different salts, but not in 1,4-dioxane (dioxane). Combined with MD simulations, these results indicate that the AA units are the main cause of aggregation through intermolecular hydrogen bonding, with additional stabilization by the central TTC. The block copolymer chains self-assemble in dioxane by adding cadmium acetate, originating flowerlike inverse micelles with a cadmium acrylate core and the TTC groups in the outer surface of the PS corona. The micelles were used as nanoreactors in the templated synthesis of a single cadmium selenide (CdSe) quantum dot (QD) in the core of each micelle, whereas the shell TTC groups can be converted into thiol functions for further use of these units in hierarchical nanostructures. Only in dioxane where simulations and SEC-MALS suggest an absence of copolymer aggregates prior to cadmium acetate addition do well-dispersed and highly luminescent CdSe QDs form by templated synthesis. These results provide valuable insights into the self-assembly of RAFT copolymers in different solvent systems as it relates to the preparation of emissive QDs with polymer-spaced thiol functionality for binding to gold nanostructures.
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Metal nanoparticles can either quench or enhance the emission of dyes in their vicinity, but the precise measurement and understanding of this effect is still hindered by experimental artifacts, especially for particles in colloidal dispersion. Here, we introduce a new methodology to correct the inner filter effect of the metal on the dye emission. To test the method, we developed new hybrid nanoparticles with a gold core and a silica shell of precise thickness (tuned from 7 to 13 nm), with a high quantum yield perylenediimide dye on the surface. This novel approach effectively avoids fluorescence quenching, allowing us to measure emission enhancements of 5 to 30 times, with no change on the dye fluorescence lifetime. Being able to measure the emission enhancement in dye-metal hybrid nanoparticles in dispersion, free from inner filter and quenching artifacts, offers excellent prospects to guide the development of more efficient fluorescent probes, sensors and photonic devices.
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Silica nanostructured materials are important in many fields, including catalysis, imaging, and drug delivery, mainly due to the versatility of surface functionalization that can bestow a huge variety of chemical and physical properties. With most applications requiring precise control over this surface modification, characterization of surface composition and reactivity have become of extreme importance. We present a novel approach to track silica surface modification and quantify functional group coverage using only solution NMR. We test the method using different types of silica nanoparticles and surface modifications, to show that after dissolving the silica matrix, the 1H NMR spectra can be resolved for every single component of the mixture. By using an internal standard, we are able to quantify the density of ligands and follow their sequential modification. Our work presents a fast, accurate, and straightforward method for surface characterization of silica nanostructures, using widely available NMR spectroscopy and small amounts of sample.
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Metal binding to natural soft colloids is difficult to address due to the inherent heterogeneity of their reactive polyelectrolytic volume and the modifications of their shell structure following changes in e.g. solution pH, salinity or temperature. In this work, we investigate the impacts of temperature- and salinity-mediated modifications of the shell structure of polymeric ligand nanoparticles on the thermodynamics of divalent metal ions Cd(ii)-complexation. The adopted particles consist of a glassy core decorated by a fine-tunable poly(N-isopropylacrylamide) anionic corona. According to synthesis, the charges originating from the metal binding carboxylic moieties supported by the corona chains are located preferentially either in the vicinity of the core or at the outer shell periphery (p(MA-N) and p(N-AA) particles, respectively). Stability constants (KML) of cadmium-nanoparticle complexes are measured under different temperature and salinity conditions using electroanalytical techniques. The obtained KML is clearly impacted by the location of the carboxylic functional groups within the shell as p(MA-N) leads to stronger nanoparticulate Cd complexes than p(N-AA). The dependence of KML on solution salinity for p(N-AA) is shown to be consistent with a binding of Cd to peripheral carboxylic groups driven by Coulombic interactions (Eigen-Fuoss mechanism for ions-pairing) or with particle electrostatic features operating at the edge of the shell Donnan volume. For p(MA-N) particulate ligands, a scenario where metal binding occurs within the intraparticulate Donnan phase correctly reproduces the experimental findings. Careful analysis of electroanalytical data further evidences that complexation of metal ions by core-shell particles significantly differ according to the location and distribution of the metal-binding sites throughout the reactive shell. This complexation heterogeneity is basically enhanced with increasing temperature i.e. upon significant increase of particle shell shrinking, which suggests that the contraction of the reactive phase volume of the particulate ligands promotes cooperative metal binding effects.
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Particles consisting of a glassy poly(methyl methacrylate) core (ca. 40 nm in radius) decorated with a poly(N-isopropylacrylamide) anionic corona are synthesized using either methacrylic acid (MA) or acrylic acid (AA) as reactive comonomers in the shell. The different reactivity ratios of MA and AA toward N-isopropylacrylamide originates p(MA-N) and p(N-AA) particles with carboxylate charges supposedly located, preferentially, in the close vicinity of the core and at the shell periphery, respectively. The corresponding swelling features of these nanoparticles are addressed over a broad range of pH values (4 to 7.5), NaNO3 concentrations (3 to 200 mM), and temperatures (15 to 45 °C) by dynamic light scattering (DLS) and small angle neutron scattering (SANS). DLS shows that the swelling of the particle shells increases their thickness from â¼10 to 90 nm with decreasing temperature, ionic strength, or increasing pH, with the effect being more pronounced for p(N-AA) whose lower critical solution temperature is shifted to higher values compared to that of p(MA-N). Potentiometric titration and electrokinetic results further reflect the easier dissociation of carboxyl groups in p(N-AA) and a marked heterogeneous interfacial swelling of the latter with decreasing solution salt content. The DLS response of both particles is attributed to the multiresponsive nature of a peripheral dilute shell, while SANS only probes the presence of a quasi-solvent-free dense polymer layer, condensed on the core surface. The thickness of that layer slightly increases from â¼6 to 9.5 nm with increasing temperature from 15 to 45 °C (at 15 mM NaNO3 and pH 5) due to the collapse of the outer dilute shell layer. Overall, results evidence a nonideal brush behavior of p(MA-N) and p(N-AA) and their microphase segregated shell structure, which supports some of the conclusions recently formulated from approximate self-consistent mean-field computations.
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Poly(butyl methacrylate) nanoparticles encapsulating a silica precursor, tetraethoxysilane (TEOS), were synthesized by a two-step emulsion polymerization process. We show that TEOS remains mostly unreacted inside the nanoparticles in water but acts both as a plasticizer and cross-linker in films cast from the dispersions. The diffusion-enhancing plasticizing effect is dominant at annealing temperatures closer to the glass-transition temperature of the polymer, and sol-gel cross-linking reactions predominate at higher temperatures. By choosing an appropriate annealing temperature, we were able to balance polymer interdiffusion and silica cross-linking to obtain films with good mechanical properties and excellent chemical resistance. The hybrid cross-linked films produced from these novel "smart" nanoparticles can be used in water-borne environmentally friendly coatings for high-performance applications.
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High performance functional coatings, based on hybrid organic/inorganic materials, are being developed to combine the polymer flexibility and ease of processing with the mechanical properties and versatility of inorganic materials. By incorporating silica nanoparticles (SiNPs) in the polymeric matrices, it is possible to obtain hybrid polymer films with increased tensile strength and impact resistance, without decreasing the flexural properties of the polymer matrix. The SiNPs can further be used as carriers to impart other functionalities (optical, etc.) to the hybrid films. By using polymer-coated SiNPs, it is possible to reduce particle aggregation in the films and, thus, achieve more homogeneous distributions of the inorganic components and, therefore, better properties. On the other hand, by coating polymer particles with silica, one can create hierarchically structured materials, for example to obtain superhydrophobic coatings. In this review, we will cover the latest developments in films prepared from hybrid polymer/silica functional systems.
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In this work, the impact of electrostatics on the stability constant, the rate of association/dissociation, and the lability of complexes formed between Cd(II), Pb(II), and carboxyl-modified polymer nanoparticles (also known as latex particles) of radius â¼ 50 nm is systematically investigated via electroanalytical measurements over a wide range of pHs and NaNO3 electrolyte concentrations. The corresponding interfacial structure and key electrostatic properties of the particles are independently derived from their electrokinetic response, successfully interpreted using soft particle electrohydrodynamic formalism, and complemented by Förster resonance energy transfer (FRET) analysis. The results underpin the presence of an â¼0.7-1 nm thick permeable and highly charged shell layer at the surface of the polymer nanoparticles. Their electrophoretic mobility further exhibits a minimum versus NaNO3 concentration due to strong polarization of the electric double layer. Integrating these structural and electrostatic particle features with recent theory on chemodynamics of particulate metal complexes yields a remarkable recovery of the measured increase in complex stability with increasing pH and/or decreasing solution salinity. In the case of the strongly binding Pb(II), the discrepancy at pH > 5.5 is unambiguously assigned to the formation of multidendate complexes with carboxylate groups located in the particle shell. With increasing pH and/or decreasing electrolyte concentration, the theory further predicts a kinetically controlled formation of metal complexes and a dramatic loss of their lability (especially for lead) on the time-scale of diffusion toward a macroscopic reactive electrode surface. These theoretical findings are again shown to be in agreement with experimental evidence.